Circuit arrangement



Sept. 28, 1943. G. HEPP CIRCUIT-ARRANGEMENT Filed July 8, 1941 2 Sheets-Sheet 1 Sept. 28,1943. G. HEPP 2,330,582

CIRCUIT-ARRANGEMENT Filed July 8, 1941 2 Sheets-Sheet 2 Patented Sept. 28, 1943 CIRCUITARRANGEMEN'I Gerard Hepp, Eindhoven, Netherlands; vested in the Alien Property Custodian Application July 8, 1941, Serial No. 401,532 In the Netherlands July 20, 1940- '7 Claims.

This invention relates to a circuit for supply ing electric oscillations to a load, said oscillations being generated or amplified by an oscillator or amplifier respectively comprising discharge tubes.

If such a circuit has to be in continuous use it is necessary to provide for a spare oscillator, or amplifier, which is put into service in the case of a disturbance of the oscillator or amplifier normally in use. Thus, for example, it is com- 1 mon practice in carrier-wave telephony systems comprising a plurality of speech channels toderive the carrier Waves required for the various channels from a common carrier-wave generator, for example by frequency multiplication. In order to ensure that in the event of a disturbance in the said carrier-wave generator whereby the latter stops oscillating or only generates oscillations having a reduced amplitude the whole of the channels may not become unserviceable, provision must be made for a spare carrier-wave generator which comes into play automatically and thus permits the operation to proceed without interruption. y

As an example of a circuit including an amplifierv which has to be in continuous use, we may mention a telephone transmitting system comprising amplifiers included in a transmission line. In the case of a disturbance, for example due to one or the amplifier valves becoming defective, it is necessary for the defective amplifier to be replaced automatically by a reserve amplifier.

According to the invention, in a circuit arrangement including two oscillators or amplifiers comprising discharge tubes and a load in which the oscillator or amplifier from which the load is normally supplied is replaced by the other in the event of a disturbance, the two oscillators or amplifiers are so arranged that an at least transient variation of one of the operating voltages or one of the electric constants of one of the oscillators or amplifiers results in a sudden permanent change of its operating condition.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference 1: the accompany drawings.

Figure 1 is a circuit arrangement of an oscillator embodying the invention,

Fig. 2 is a graph showing the relation between the amplitude of the oscillations generated in the circuit of Fig. 1 and the grid bias of the discharge tube thereof,

' Fig. 3 is a schematic diagram of a circuit according to one embodiment of the invention,

Fig. 4 is a schematic" diagram of a circuit according to a second embodiment of'theinvention, Fig. 5 is a schematic diagramlof a circuit which is a modification of [the circuit arrangement shown in Fig. 1, and I t Fig. 6 is a schematic diagram of a circuit according to another embodiment of the invention. Fig. 1 shows a circuit arrangement of an oscil lator comprising a backcoupled discharge tube I. The grid circuit of this tube includes an oscillatory circuit 2 which is'coupled inductively to the anode circuit by means of afeedback coil.

3. In addition, the cathode lead includes resistances 4 and 5 shunted-by a condenser 6 which substantially forms a by-pass for the oscillations to be generated. These resistances arein series with a resistance] connected to the source of. anode voltage8 and so proportioned that the voltage drop bringsabout such a negative grid bias that the tube I is disrupted and the circuit does not oscillate. Connected in parallel with the resistance 5 is a switch 9 and a resistance I0 which is shunted by a condenser E I. When this switch 9 is closed the negative grid bias is reduced to 'suchextent that the circuit starts oscillating. By correct adjustment of thecircuit it may be ensured thatthe oscillations are maintained even afterthe switch 9 is reopened. If, however, the mutual conductance of the tube'l decreases either from age or by reduction of one ofthe supply voltages the circuit stops oscillating and the oscillations do not restart spontaneouslyfleven after the tube-is renewed or the supply voltages have reassumed their normal value.

In order thatjthe operationdescribed above may be clearly understoodFig. 2 shows the con nection between the grid bias'o of the tube-I and the amplitude i of the generated oscillations.

At low values of. the grid bias, no oscillations are generated at all. If, however, the biasis in creased to a value'v the circuit suddenly starts oscillating, the amplitude of theggenerated oscila lations being'i'; On further increase of the grid bias the amplitude of thegenerated oscillations increases so as to give the curve ab; If the grid bias is then reduced the amplitudjde'creases so as to give the curve be and atc 'suddenlyjumps I from the valuez'" to zero.

In the circuit shown in Fig. l with the switch 9 open the grid bias is adjusted to avalue v comlprised between 22g" and 12 at which oscillations do not start spimtaneously. on the switch 9 being closed fora short time the grid'bias is increased instantaneouslyto the value in or higher so that the switch tube startsoscillating. After At the same time, the mean anode The same effor example if the mutual conductance of the tube decreases.

It follows from the above that the oscillator circuit is thus so arranged and adjusted that an at least transient variation of one of the operating voltages results in a sudden permanent change of the operating condition, that is to say that an inoperative oscillator is rendered operative after a transient increase of the grid voltage, whereas after a variation of one of the operating voltages or one of the electric constants resulting in a decrease of the amplitude of the oscillatlons generated the oscillator is rendered inoperative.

Fig. 3 shows two of such oscillators, similar reference numerals to those employed in Fig. 1

designating similar components; the components of the oscillator [3 shown on the right in the figure are distinguished by accents from those of the left hand oscillator l2.

The anode circuit of the oscillator l3 includes a relay l5 which is shunted by a condenser I l and operates a switch I6. On this relay being energized by the anode current of the tube I, the switch l6 connects to the right so that the load, which is connected to the terminals l8 and l9, receives energy from the oscillator l3 via a coil ll coupled'to coil 3'.

It is assumed that theoscillator l2'also generates oscillations but it cannot deliver energy to the load by this time. If, however, due to a disturbance the oscillator i3 is rendered inoperative in the manner described above with reference to Fig. 1 the relay I 5 is lie-energized due to the d crease of the mean anode-direct current, the switch l6 takes up the position shown and the oscillator J2 delivers energy to the load via the anode coil 3 and the coupling coil l1.

It follows that" these oscillators are so connected that the variation of the mean anodecurrent caused by the cessation of oscillations in the oscillator initially supplying the load brings about the change of connections necessary" to connect the load to the spare oscillator.

Fig. 4 shows a further embodiment of the invention. The circuit arrangement is substantially similar to that of Fig. 3, however the oscillator l2 has added to it a relay 2B which controls contacts 23, and 26, a relay 2i which controls contactsl-l, 9 and 21 and the relay 22 which controls contacts [6; and the oscillator l3 has a relay l5 which operates contacts 24 and 28. "All contacts are shown in off position that is tos'ay in the position in which the associated relay is not energised. In additiomthe circuit includes two alarm circuits A andB, the alarm circuit A V serving to give an alarm when the oscillator normally in use (the main oscillator) is thrown out of use and the connections are changed to' the reserve oscillator, whereas the alarm circuit'B serves to give an urgent alarm when both oscillators are rendered inoperative.

The oscillator I2 is the main oscillator, I3 is the reserve oscillator; both are in continuous use.

Since both oscillators operate the relays 20 and I5 are energised under the influence of the mean anode currents; the contacts 23 and 24 are closed, whereas the contacts 25, 26 and 23 are open.

- Due to the contacts 26 and 28 being open the alarm circuit A is not in use. Relay 2! is energised due to the contacts 23 and 24 being closed; the contacts 9, 9' and 2'! are consequently open; since contact 2'! is open the urgent alarm circuit is also open.

Due to the relay 22 not being energised on account of contact 25 being open, contact l6 cccupiesthe position shown and the load is coupled to the oscillator l2.

Thus, if one of the above-mentioned effects is responsible for a disturbance in the oscillator l2 with the result that the latter is disrupted the energisation of relay 20 is suppressed due to the decrease of the mean anode current with the result that contacts 25 and 25 are closed and contact 23 is opened.

Thus, the following effect occurs: alarm is given due to the closure of 26; due to the closure of 25 the relay 22 is energised so that it changes the connections of contact 16 and couples the load to the oscillator l3. The opening of 23 has no further result.

In the event of oscillator l3 also being disrupted with the result that the energisation of relay l5 disappears the contact 24 is opened so that the energisation of 2| disappears, contact 2'! is closed and urgent alarm is given in the circuit B.

Obviously, the same effect occurs when both oscillators are thrown out of use simultaneously, for example due to a disturbance in the common supply voltage.

Due to relay 2| being de-energised the contacts 9 and 9' are also closed and this results in the negative grid bias being so reduced that on the return of the supply voltage both oscillators again become operative. This results in the relays 20 and I5 being re-energised and the contacts 9 and 9' being re-opened. Thus, the circuit arrangement of Fig. 3 ensures that if both oscillators are rendered inoperative due to the absence of at least one of the supply voltages a change of connections occurs under the influence of the mean anode currents of a discharge tube so that both oscillators are transformed into such a condition that at least one delivers energy to the load upon thereturn of the missing supply voltage.

Properties similar to those possessed by the circuit of Fig. 1 can be obtained by means or" the circuit of Fig. 5, similar reference numerals to those employed in the previous figures again designating similarcomponents. In this circuit arrangement the anode coil 3 is coupled to a coil 29, which supplies part of the output energy to a rectifier 39. The rectified voltage thus obtained, which is set up across a resistance It, is used to .decrease the negative grid bias which. occurs across the resistances 4 and 5.

This circuit arrangement operates as follows: The high negative bias which is set up across the resistances 4 and 5 prevents the tube I from generating oscillations. If the switchB is closed for a short time the operating point of the tube 23'. This voltage is'rectified byther'ectifier 3i)v so that acompensating voltage is setup across the resistance l which displaces the operating point of tube '"l to such: extent that oscillations are permanently-generated. If, however, due to a disturbance; for example, the supply voltage falls below a given value the amplitude'of the generated oscillations decreases, the compensating gridopened. This circuit also may beembodied in a selective switching arrangement such'a's shown inFig.4.- a

- In thecircuit rangement causing'a decrease in the amplitude of voltage" across the resistance IU- decreases and the negative grid bias of the tube I is increased.- Thus, the amplitude of the generated oscillations is "again reduced and so forth so that eventually the tube is thrownout of operation.

In this circuit arrangement care should be taken that an increase of thegrid bias does not result in an increase of thea'mpli-tude of the generated'oscillations as otherwise the circuit would start oscillating at intervals; and this must be avoided. If this requirement is notsatisfied, a stabilising element must be included in'the cir'-' cuit, for examplea voltage limiter; such'as a glow discharge lamp in parallel with the resistance Ill.

The principle adopted in the oscillator-circuit of- Fig. 5 can also be employed with-amplifiers.

Two cases have 'to be distinguished. In'one case the oscillations tobe amplified contain a component of constant value and frequency, such as occurspfor example, with "amplifiers for carrier-wave telephony.- In this case an alternating voltage of constant value can be derived from the output side of the amplifier and be supplied to a rectifier on the principle illustrated by Fig. 5. In the second case, in which there is no component that remains constant, such for exampleas with amplifiers for speech or music, the same effect'may be obtained by means o'f'an auxiliary oscillation lying outside the frequency band and supplied to the grid of one of the tubes, and this will be described more fully with reference to Fig.6.

Fig. 6 shows a two-stage resistance-coupled amplifier in which in the manner mentioned before and by means of the component members 4, 5, 6, '1, l0 and H the tube l is given such a high negativebiasthat it'is disrupted. The oscillations to be amplified, which are received for examplevia a telephone line, are fed, with the in terposition of a low-frequency transformer 32, to the gridof tube I and inaddition an auxiliary oscillation having a frequency lying outside the band tobe amplified and a constant amplitude is transmitted to the said grid with the interposition of a transformer 33. The tube 50 is coupled to the anode circuit of tube l by means of the usual condenser 34 and resistance 35. The tube 50 receives a negative bias by way of a cathode resistance 36 shunted by a condenser 31.

To'the output circuit of the tube 53 is connected for'example a telephone line 38 with the interposition of an output transformer 39. The primary ofthe output transformer is shunted by a condenser 40. The output circuit also includes a circuit 4| tuned to the auxiliary oscillation; the oscillations that may occur in this circuit induce an alternating voltage in a coil 42 and this voltage is rectified by 30 so that a direct voltage is applied to the resistance It.

For putting the circuit into service, the switch 9 is closed for a short time, the adjustment of the tube being normal, and both the oscillations fed by the transformer 32 and those fed by the transformer 33 are amplified'by the arrangement. As a consequence of the direct voltage set up across the resistance ID by the circuit 4|, the coil 42 and the rectifier 33 the normal adjustment of the the amplified oscillations, produces a corresponding decrease inthe compensating voltage set up across the resistance It. "This decrease in voltage across resistance 40 makes the voltage applied tothe control grid'of the tube lbmore negative so that the-tube is adjusted to a more unfavorable operating condition which in turn further reduces the amplitude of the amplified voltages. As -a-- consequence of the cumulative action so produced, the circuit is automatically thrown out of operation.

Thus the circuits shown in .Figs. '5 and 6 have the propertythat' upon aitransient decrease in the value of a grid voltagewhich normally blocks operation of the tube oscillations are generated or amplified continuously; Furthermore; thegenerated or amplified oscillations provide" a compensating voltage which at least partly suppresses the blocking voltage. Upon an at least transient change of one of the operating voltages or one of the electric constants of the circuit, the compensating voltagedecreases in value thereby decreasing the amplitude of the generated or amplified'oscillations which in turn further decreases the value of the compensating voltage. This action is curnulativeand the oscillator or amplifier is'rapidly rendered inoperative.

Whatlclaimis:

oscillations to a' load comprising a circuit for nor-' mally supplying oscillations to the load including r load upon failure of said first circuit,-eachof said circuits including means associated with the control electrode. of the discharge tube tc'produce a suddenand permanent change in the operatingcondition of the circuit upon the occurrence of an at least transient variation in the operating voltage or' electric constants of the discharge tube. I

2. A circuit arrangement for supplying electric oscillations to afloadcomprising a supply circuit for normally supplying the oscillations to the load including an oscillatory circuit containing a dis chargetube having acontrol electroda'a second supply circuit for supplying the oscillations'to the load upon failure of said first circuit and including an oscillatorycircuit containing a discharge tube having a control electrode,'means to connect said second supply circuit to the load upon failure of said1 first supply circuit, each of said supply circuits including means associated with the control electrode of the discharge tube to produce a sudden and permanent change in the operating condition of the circuit upon the occurrence of an at least transient variation in the operating voltage or the electric constants of the circuit, said latter means including a circuit for applyingto the control electrode a negative grid bias of a value at which an at least transient in.- crease thereof will cause the continuous generation of oscillations and at which at least transient changes of one of the operating voltages or tube l subsists 1 even when} the switch "9 is re v of Fig gfi a-disturbance such as a variation in'the electric constants of the ar- 1 A circuit arrangement for supplying electric of one of the'electric constantsof the circuit will:-

make the supply circuitinoperative.

3. A circuit arrangement for supplying electric oscillations to a load comprising a circuit fornormally supplying oscillations to the loadincluding a discharge tube havinga control, electo make the circuit inoperative,- means to suppress said blocking voltage tothereby permit the con-- tinuous production ofoscillations, and means controlled by the produced oscillations to obtain a compensating voltage which at least partly suppresses the blocking voltage and'means controlled by an at least transient change in theoperating voltage or one'ofthe electric constants of the cir-- cult to cause the compensating voltage to decrease so rapidly as to render the circuit inoperative.

4; A circuit arrangement for supplying electric oscillations to a load comprising. a circuit: for normally supplying oscillations to the load including a discharge tube having a control electrode, a second circuitfor supplying oscillations to the load upon failure of said first circuit and including a discharge tube having. a control electrode, means to connect said second circuit to the load upon failure of said first circuit,.each of said circuits including means associated with the control electrode of the discharge tube to produce a sudden and permanent change in the operating condition of the circuit upon the occurrence of an at least transient variation in the operating voltage or electric constants of the discharge tube, and means controlled by variations in the mean anode current of-the discharge tube of one of said circuits to connect the other circuit to the load when the first circuitbecomes inoperative.

5. A circuit arrangement forsupplyingelectri'c oscillations to a load comprising a circuit for normally supplying oscillations to the load in,- cluding a discharge tube having a controlelectrode, and a supply voltage, a secondcircuit for supplying oscillations to the loadupon'failure of said first circuit and including a discharge tube having a control electrode, and a supply voltage, means to connect said second circuit to the load upon failure of said first circuit; each of said cir= cuits including means associatedwith the con trol electrode of the discharge tube to'pro'duce a sudden and permanent change in the'operating condition of the circuitupon'the occurrence of an at least transient variation'inthe operating voltage or electric constants of the discharge tube, and means controlled by the mean anode current of one of the discharge tubeswhen both circuits are inoperative due to failure ofatleast on of: the supply voltages to, place at least one ofsaid circuits in-condition to supply; energy to the load: when the supply voltage returns.

6. A= circuit arrangement'forsupplying electric oscillations, to-a' load comprising a supply circuitfor normally supplying the oscillations to the, load including an oscillatory circuit containing adischargetube having, a control electrode; a second supply circuit; for supplyingthe oscilla tionsto the load upon failure of' said first circuit and; including an oscillatorycircuit containing a discharge tube havinga control electrode,-means to connect said second supply circuit to the load upon failureof said first supply circuit, each of said supply circuits including means associated with the control; electrode-of the discharge tube to produce a sudden and permanent change in the operating condition of; the circuit uponthe occurrence of an at least; transient variation in the operating voltage or the electric constants of the circuit, said latter meansincluding a cite cuit for applying to the control electrode a nega: tive gridbiasof a value atwhich an at least transient increase thereof will cause the, contin-lnous generation of oscillations and at which at least transient changes of enact the operating voltages or ofoneofthe electric constants-of the circuit will make the supply circuitinoperative, and means controlled by a change in mean anode current of the discharge tube of said first circuit to indicatewhenthe circuit becomes in operative.

7. A circuit arrangementfor supplying electric oscillations to'a load comprising a supply circuit for normally supplying the oscillations to the loadincluding an oscillatory circuit containing a discharge tube having-a control electrode, a second supply circuit for supplying theoscillationsto the loadupon' failure of said first cire cuit and including an oscillatory circuit containinga discharge tube. having a control electrode means to connect said second supply circuit to the load upon failure of said first supply circuit, each of said supply circuits including means associated with the control electrode of the discharge tube toproduce asudden and permanent change in the operating condition of the circuit upon the-occurrence Oran at least transient variation in the operating voltag or the electric constants of the circuit, said latter means including a circuit for applying-to the control electrode a negative grid bias oi-a value at which'an at leasttransient increase thereof will cause the continuous generation of oscillations and atwhich at least transient changes of one of the operatingvoltages or of one of the electric constants of the circuit will make the supply inoperative,- and means controlled'bythe change in the mean anode currents of the discharge tubes of both circuits-to indicate a dis-' ruption of both circuits.

GERARD HEPP. 

